int libvchan_wait(libvchan_t *ctrl) {
int ret = -2; /* invalid, so can be distinguished from real
libxenvchan_wait return code */
struct xs_handle *xs;
if (ctrl->xenvchan->is_server && libxenvchan_is_open(ctrl->xenvchan) == 2) {
/* In case of vchan server waiting for a client, we'll not receive any
* notification if the remote domain dies before connecting. Because of
* that, check periodically if remote domain is still alive while
* waiting for a connection. Actually this doesn't cover all the cases
* - if remote domain is still alive, but remote process dies before
* connecting, we'll also not receive any notification. But this, in
* most cases, can be solved by application using libvchan.
*
* During normal operation this shouldn't be long - in most cases vchan
* client will connect almost instantly. So this sleep(10) loop will
* not hurt. Alternativelly it could be implemented with
* xs_watch("@releaseDomain"), but such approach will slow down most
* common execution path (xs_open+xs_watch even if client connects
* right away).
*/
while (ret == -2 && libxenvchan_is_open(ctrl->xenvchan) == 2) {
fd_set rd_set;
struct timeval tv = { 10, 0 };
int vchan_fd = libxenvchan_fd_for_select(ctrl->xenvchan);
FD_ZERO(&rd_set);
FD_SET(vchan_fd, &rd_set);
switch (select(vchan_fd+1, &rd_set, NULL, NULL, &tv)) {
case 0:
if (!libvchan__check_domain_alive(ctrl->xc_handle, ctrl->remote_domain))
return -1;
break;
case 1:
/* break the loop */
ret = -1;
break;
default:
if (errno == EINTR)
break;
perror("select");
return -1;
}
}
}
ret = libxenvchan_wait(ctrl->xenvchan);
if (ctrl->xs_path) {
/* remove xenstore entry at first client connection */
xs = xs_open(0);
if (xs) {
/* if xenstore connection failed just do not remove entries, but do
* not abort whole function, especially still free the memory
*/
xs_rm(xs, 0, ctrl->xs_path);
xs_close(xs);
}
free(ctrl->xs_path);
ctrl->xs_path = NULL;
}
return ret;
}
int libvchan_is_open(libvchan_t *ctrl) {
int ret;
struct evtchn_status evst;
ret = libxenvchan_is_open(ctrl->xenvchan);
if (ret == 2) {
if (!libvchan__check_domain_alive(ctrl->xc_handle, ctrl->remote_domain))
return VCHAN_DISCONNECTED;
return VCHAN_WAITING;
}
if (!ret)
return VCHAN_DISCONNECTED;
/* slow check in case of domain destroy */
evst.port = ctrl->xenvchan->event_port;
evst.dom = DOMID_SELF;
if (xc_evtchn_status(ctrl->xc_handle, &evst)) {
perror("xc_evtchn_status");
return VCHAN_DISCONNECTED;
}
if (evst.status != EVTCHNSTAT_interdomain) {
if (!ctrl->xenvchan->is_server)
ctrl->xenvchan->ring->srv_live = 0;
return VCHAN_DISCONNECTED;
}
return VCHAN_CONNECTED;
}
libvchan_t *libvchan_client_init(int domain, int port) {
char xs_path[255];
char xs_path_watch[255];
libvchan_t *ctrl;
xc_interface *xc_handle;
struct xs_handle *xs;
char **vec;
unsigned int count, len;
char *dummy = NULL;
char *own_domid = NULL;
xc_handle = xc_interface_open(NULL, NULL, 0);
if (!xc_handle) {
/* error already logged by xc_interface_open */
goto err;
}
/* wait for server to appear */
xs = xs_open(0);
if (!xs) {
perror("xs_open");
goto err_xc;
}
len = 0;
if (!xs_watch(xs, "domid", "domid")) {
fprintf(stderr, "Cannot setup xenstore watch\n");
goto err_xs;
}
if (!xs_watch(xs, "@releaseDomain", "release")) {
fprintf(stderr, "Cannot setup xenstore watch\n");
goto err_xs;
}
while (!dummy || !len) {
vec = xs_read_watch(xs, &count);
if (vec) {
if (strcmp(vec[XS_WATCH_TOKEN], "domid") == 0) {
/* domid have changed */
if (own_domid) {
free(own_domid);
own_domid = NULL;
xs_unwatch(xs, xs_path_watch, xs_path_watch);
}
}
free(vec);
}
if (!own_domid) {
/* construct xenstore path on first iteration and on every domid
* change detected (save+restore case) */
own_domid = xs_read(xs, 0, "domid", &len);
if (!own_domid) {
fprintf(stderr, "Cannot get own domid\n");
goto err_xs;
}
if (atoi(own_domid) == domain) {
fprintf(stderr, "Loopback vchan connection not supported\n");
free(own_domid);
goto err_xs;
}
snprintf(xs_path, sizeof(xs_path), "/local/domain/%d/data/vchan/%s/%d",
domain, own_domid, port);
/* watch on this key as we might not have access to the whole directory */
snprintf(xs_path_watch, sizeof(xs_path_watch), "%s/event-channel", xs_path);
if (!xs_watch(xs, xs_path_watch, xs_path_watch)) {
fprintf(stderr, "Cannot setup watch on %s\n", xs_path_watch);
free(own_domid);
goto err_xs;
}
}
dummy = xs_read(xs, 0, xs_path_watch, &len);
if (dummy)
free(dummy);
else {
if (!libvchan__check_domain_alive(xc_handle, domain)) {
fprintf(stderr, "domain dead\n");
goto err_xs;
}
}
}
if (own_domid)
free(own_domid);
xs_close(xs);
ctrl = malloc(sizeof(*ctrl));
if (!ctrl)
return NULL;
ctrl->xs_path = NULL;
ctrl->xenvchan = libxenvchan_client_init(NULL, domain, xs_path);
if (!ctrl->xenvchan) {
free(ctrl);
return NULL;
}
ctrl->xenvchan->blocking = 1;
/* notify server */
xc_evtchn_notify(ctrl->xenvchan->event, ctrl->xenvchan->event_port);
ctrl->remote_domain = domain;
ctrl->xc_handle = xc_handle;
return ctrl;
err_xs:
xs_close(xs);
err_xc:
xc_interface_close(xc_handle);
err:
return NULL;
}
